Variable output centrifugal pump

ABSTRACT

A variable output pump assembly includes an input drive member and a primary pump member operatively driven thereby. A second drive member supplements the pump assembly. A magnetic coupling is interposed between the input drive member and the second drive member to variably drive the pump assembly.

BACKGROUND

The present disclosure relates to a pump, pump assembly, or pump system, and an associated method of magnetically coupling between an input drive member and an output driven member. It finds particular application in conjunction with a variable output pump, for example a centrifugal pump, that finds specific use in a fuel pump application, and will be described with reference thereto. However, it is to be appreciated that the present exemplary embodiment is also amenable to other like applications that encounter similar problems or require similar solutions.

High speed centrifugal (HSC) pumps typically encounter two problem areas when attempting to apply them to main engine fuel pump applications. First, at low starting speeds (for the engine) the centrifugal pump does not produce sufficient pressure to supply the fuel system for the start function. Second, once running, the centrifugal pump tends to over-generate pressure at operating conditions such as idle and cruise thereby wasting energy and increasing system operating temperatures.

This disclosure remedies both of these problems in a simple, reliable, effective, and inexpensive manner.

BRIEF DESCRIPTION

A variable output pump assembly includes an input drive member and a primary pump member operatively driven thereby. A second drive member supplements the pump assembly. A coupling is interposed between the input drive member and the second drive member to variably drive the pump assembly member.

The coupling is preferably a variable magnetic coupling interface between the input drive member and the second drive member.

The magnetic coupling interface includes a magnet and a magnet/ferro-magnetic member in spaced relation and the spacing therebetween is selectively altered to vary the magnetic coupling strength therebetween.

A primary advantage is the ability to reduce energy needs during certain operating conditions (e.g., cruise and idle).

Another benefit is associated with limiting the temperature increase to the system.

Another advantage is efficiently transmitting torque to the pump assembly.

Another benefit resides in adding normally lost torque to the output shaft and thereby improve torque transmission capability.

Still another advantage is associated with being able to generate additional pressure at desired operating conditions (e.g., engine start and take-off), and once running, to decrease the pressure.

Still other benefits and advantages will become apparent those skilled in the art after reading and understanding the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a first embodiment of a variable output centrifugal pump assembly.

FIG. 2 is a table providing exemplary characteristics of the variable output centrifugal pump assembly of FIG. 1.

FIG. 3 is a schematic representation of a second embodiment of a variable output centrifugal pump assembly.

FIG. 4 is a schematic view of the FIG. 3 embodiment taken generally along the lines 4-4 of FIG. 3.

FIG. 5 is a schematic view of the embodiment of FIG. 3 taken generally along the lines 5-5 of FIG. 3.

DETAILED DESCRIPTION

With reference to FIG. 1, a variable output pump, pump assembly, or pump system (which terms may be used interchangeably herein), and more specifically a variable output centrifugal pump system, 100 is shown. A centrifugal pump 110 includes a fluid inlet 112 so that fluid (such as jet fuel for use in an aircraft engine, although this use is not intended to be limiting) is supplied to a primary impeller 114 rotatably received in housing 116. The primary impeller 114 is driven by an input drive or drive shaft 118 rotating at a rotational speed ω_(ring) as is conventional in the art and thus rotates at the same rotary speed ω_(ring) as the input drive. The primary impeller 114 imparts energy to the fluid (e.g., increases the pressure of the fluid) which pressurized fluid exits generally radially from the primary impeller.

In addition, a secondary impeller 130 receives the pressurized fluid exiting the primary impeller 114 and imparts further energy to the fluid (again, further increases the pressure of the fluid). The secondary impeller 130 is schematically illustrated as part of the rotating housing 116 that receives the primary impeller 114, although the secondary impeller and housing could be separate components as will be readily recognized by one skilled in the art. The housing 116 and thus the secondary impeller 130 rotate at a same rotary speed ω_(sun) whereby the additional energy is added to the fluid before the pressurized fluid enters into a radial diffuser/collector (not shown).

The rotational speed of the secondary impeller 130 may be varied relative to the input drive shaft 118 to vary the amount of additional energy (additional pressure) added to the fluid. In a first preferred arrangement, this variable output is achieved with a variable magnetic coupling interface, such as a magnetically coupled planetary gear transmission 140, between the input drive shaft 118 and a secondary drive member 142 such that these drive components 118 and 142 (shown in a preferred concentric arrangement) can rotate at different rotational speeds. The magnetically coupled planetary gear transmission 140 is operatively connected to the input drive and configured for or capable of transmitting a variable speed drive to the secondary impeller 130. That is, depending on the gearing and the amount of drive torque transmitted through the magnetically coupled planetary gear transmission 140, the secondary impeller 130 will rotate at the same or a different rotational speed as the input drive 118, and can be easily transitioned to a different rotational speed as will become apparent below.

More particularly, in one arrangement, the magnetic coupling 140 includes a planetary gear set carrier 148 that varies the output speed of a sun gear 146 which is attached to the secondary impeller 130 via the secondary drive member 142. The torque balance of the secondary impeller load and magnetic coupling strength (as carried through the planetary gear ratio) sets the output rotational speed of the secondary impeller 130 and thus its level of output pressure. Control of the rotational speed of the secondary impeller 130 is achieved by varying an air gap 160 between a movable magnet 162 that is selectively moved by actuator 164 (e.g., slides along a linear axis that in the exemplary embodiment is parallel to the rotational axis of the input drive and the planetary gear set carrier 148). The actuator advances and retracts the magnet 162 relative to a magnetically coupled carrier 148 that includes a magnet or ferro-magnetic material 166 operatively associated with planets or planet gears 168 received in the gear set carrier 148. The planets 168 are, in turn, operatively engaged with the sun gear 146 that is joined to the secondary drive member or hollow shaft 142 (received around the input drive shaft 118) to drive the housing 116 and secondary impeller 130. The spacing or air gap 160 between the magnet 162 and the magnet/ferro-magnetic material 166 associated with the planets determines the amount of rotational torque that is transferred between the ring gear 144 (rotating at the same rotational speed ω_(ring) as the input drive) and the planets 168. Thus, if the air gap 160 is small, the magnetic attraction is higher and an increased ratio of the rotational speed is transferred to the planets 168 when compared to a larger air gap which results in a reduced magnetic force between the magnet 162 and the magnet/ferro-magnetic material 166 attached to or part of carrier 148, and likewise a reduced ratio of the rotational speed transferred to the planets. Thus, the rotational speed ω_(sun) of the planets 168, sun gear 146 (operatively driven by the planets 168), and consequently the secondary drive shaft 142 (operatively driven by the sun gear) can be the same as the rotational speed ω_(ring) of the input drive 118, or may be different, depending on the amount of torque transfer through the magnetic coupling achieved by varying the air gap 160 between the actuated magnet 162 and the magnet/ferro-magnetic material 166.

Changing the magnetic coupling air gap 160 results in either a speed up or slow down of the rotational speed ω_(sun) of the secondary impeller 130 relative to the rotational speed ω_(ring) of the input drive 118. The magnetic coupling mechanism 140 is preferred in this application because the speed control is readily achieved without adverse or ill failure mode effects that are potentially associated with a friction type clutch mechanism.

As can be seen from FIG. 2, changing the spacing of the magnetic coupling air gap 160 results in speeding up or slowing down of the rotational speed ω_(sun) of the secondary impeller 130 relative to the rotational speed ω_(ring) of the input drive 118. Therefore, at engine start conditions, the air gap 160 is reduced or minimized and the secondary impeller 130 can turn sufficiently fast to achieve the desired fuel system pressure for engine start. Likewise, at engine idle and cruise speeds where high system pressure may not be required, the air gap 160 is increased or maximized so that the secondary impeller 130 can be significantly slowed to minimize pump output pressure which leads to minimization of power of the input drive 118 shaft and less fuel system heat build-up. At take-off, the air gap 160 is reduced/minimized and the speed of the secondary impeller 130 is increased by minimizing the air gap 160 to provide maximized pump pressure output to meet fuel system pressure needs.

A generally related concept of a magnetic coupling interface being used to vary the speed in a transmission assembly and, for example, a transmission assembly described in connection with one specific end use, namely a centrifugal pump assembly, is shown in a second exemplary embodiment of FIGS. 3-5. Again, there is a desire to efficiently and variably transmit torque to an output shaft, and preferably provide variable speed as a supplement or secondary drive input to a pump driven by a primary input. One manner of achieving this is to use a magnetic coupling, and more specifically another version of a variable speed planetary gear transmission is illustrated and described herein. This second exemplary arrangement not only varies the speed of the output shaft (relative to the input) but also incorporates features to add “normally” lost torque in such a device to the output shaft and thereby improve torque transmission capability.

A variable speed planetary gear set 200 is a part of the magnetic coupling illustrated in FIGS. 3-5. One potential use of the variable speed planetary gear set 200 is in connection with a variable output centrifugal pump 202 that includes a rotating impeller 204 that raises pressure of the fluid between an inlet 206 and outlet 208. The variable centrifugal pump assembly 202 includes a connection between a drive member and the impeller to pressurize the fluid in the system. Here, however, details of the variable speed planetary gear set 200 are different than that shown and described in connection with the embodiment of FIGS. 1 and 2.

The input drive 210 has a rotational speed ω_(s) and drives or rotates a sun gear 212 at this same rotational speed ω_(s). The sun gear 212, in turn, drives one or more planets 214 which drive a ring gear 216 that rotates at a rotational speed ω_(r) in a manner generally known by an ordinarily skilled artisan. In addition, the planets 214 are operatively associated with a first carrier 220 that is, in turn, operatively associated with an output drive 222. Controlling a rotational speed ω_(r) of the ring gear 216 drives the output drive 222 at a desired rotational speed ω_(c).

The ring gear 216 includes a portion of a magnetic coupling 230, namely, magnets 232 are disposed in circumferentially spaced arrangement along a face of the ring gear 216. In addition, the magnetic coupling 230 includes one or more planets 234 that each have circumferentially spaced magnets or ferro-magnetic material 236. An air gap 240 is provided between the planets 234 and the magnets 232 of the ring gear 216. The air gap 240 is selectively varied, which varies the amount of torque transferred between these components, by axially moving the planets 234 toward and away from the magnets 232 of the ring gear 216. Actuator 242 axially advances and retracts the planets 234 via a second carrier 244. A spline or keyed connection 246 limits the movement of the second carrier 244 (and thus the planets 234) in an axial direction. As the air gap 240 is reduced or minimized, a greater amount of torque from the ring gear 216 is transferred to the planets 234. The torque imposed on the planets 234 is then transferred to pinion gear 250 of the first carrier 220 and thus adds torque to the output at the rotational speed ω_(c) of the output drive 222 (which is the drive member for the impeller 204).

An intentional slipping of the ring gear 216 is used to vary a resultant rotational speed ω_(c) of the first carrier 220. Specifically, controlling the rotational speed ω_(r) of the ring gear 216 drives the first carrier 220 and likewise the output drive 222 at a desired rotational speed ω_(c). More particularly, the pinion gear 250 of the first carrier 220 drives planets 234 of the second carrier 244 which mesh with the pinion gear 250. This varies the resultant speed of the first carrier 220 and thus the output drive 222. The magnetic coupling 230 flexibly transmits torque between the ring gear 216 and the planets 234 associated with the second carrier 244. If the tangential velocity of the magnets 232 of the magnetic coupling 230 connected to the ring gear 216 is greater than the tangential velocity of the magnets/ferro-magnetic material 236 connected to the planets 234, torque from the ring gear 216 will be added to the output drive 222 via the meshing of the planets 234 with the pinion gear 250.

The speed of the output shaft 222 is set by the amount of torque used to hold or slow down the ring gear 216. This torque is that which is transmitted to the output drive 222 via the flexible magnetic coupling 230. The amount of torque transmission through the magnetic coupling 230 is a function of the air gap 240 between the halves of the magnetic pair. Thus, by varying the air gap 240 via the actuator 242, the rotational speed of the output shaft 222 relative to the input shaft 210 can be varied. The air gap 240 is modulated by axial movement of the second carrier assembly 244 along the splined interface 246 with the transmission housing. The spline 246 allows the second carrier assembly 244 to slide axially while resisting the torque applied to hold the second carrier from rotating. The actuator 242 is used to slide the second carrier assembly 244 and thus set the air gap 240. An assortment of open and closed loop controls can then be imparted to provide the desire speed outcome for the transmission.

The present disclosure also contemplates that the system may employ an electromagnetic arrangement to achieve a desired speed ratio or alter the speed ratio during operation. For example, rather than employing permanent magnets and/or ferro-magnetic materials that vary the strength of the magnetic field by varying the distance between the magnetic components (e.g., using the actuator in the above-described embodiments), the strength of the magnetic field in an electromagnetic arrangement can be easily varied by changing the amount of electric current through the wire or coil. Of course, further details of the structure and operation of electromagnets are known to those skilled in the art and will not be described herein for purposes of brevity. The use of an electromagnetic arrangement, however, is yet another type of magnetic coupling that achieves the desired control of the magnetic field and likewise the associated variation in the speed ratio and torque of the output shaft of above-described planetary gear transmission, which in one embodiment is used in a centrifugal pump assembly.

A first item of the present disclosure includes a variable output pump assembly that has an input drive member, a primary pump member operatively driven by the input drive member, a second drive member, and a variable torque coupling interposed between the input drive member and the second drive member to vary speed output of the second drive member.

A second item of the present disclosure includes the coupling as a variable magnetic coupling interface between the input drive member and the second drive member, and the second item may be used in combination with the first item.

A third item of the present disclosure includes the magnetic coupling interface having a magnet and a magnet/ferro-magnetic member in spaced relation and the spacing therebetween is selectively altered to vary the magnetic coupling strength therebetween, and the third item may be used in combination with either or both of the first and second items.

A fourth item of the present disclosure includes one of the magnet and magnet/ferro-magnetic member that is operatively connected to an actuator that selectively moves the one of the magnet and magnet/ferro-magnetic member toward and away from the other of the magnet and magnet/ferro-magnetic member, and the fourth item may be used in combination with any one or more of the first through third items.

A fifth item of the present disclosure includes the input drive member connected to the primary pump member which includes a primary impeller, and a secondary pump member operatively driven by the second drive member at a speed responsive to the coupling, and the fifth item may be used in combination with any one or more of the first through fourth items.

A sixth item of the present disclosure includes a ring gear of a planetary gear assembly also operatively connected to the input drive member for rotation therewith, and the sixth item may be used in combination with any one or more of the first through fifth items.

A seventh item of the present disclosure includes a planetary gear operatively driven by the ring gear such that the secondary pump member that includes a secondary impeller operatively associated with the planetary gear assembly rotates at a different rotational speed, and the seventh item may be used in combination with any one or more of the first through sixth items.

An eighth item of the present disclosure includes the carrier receiving one of the magnet and the magnet/ferro-magnetic member, and a fixed housing assembly receives the other of the magnet and magnet/ferro-magnetic member, and the eighth item may be used in combination with any one or more of the first through seventh items.

A ninth item of the present disclosure includes the planetary gear assembly having at least one planetary gear that receives a rotational drive input from the ring gear, and drives a sun gear in response thereto, and the ninth item may be used in combination with any one or more of the first through eighth items.

A tenth item of the present disclosure includes an inlet of the secondary impeller receiving output flow from an outlet of the primary impeller, and the tenth item may be used in combination with any one or more of the first through ninth items.

An eleventh item of the present disclosure includes the magnetic coupling interface having a magnet and a magnet/ferro-magnetic member, where one of the magnet and magnet/ferro-magnetic material is located on a first portion of a planetary gear arrangement, and the eleventh item may be used in combination with any one or more of the first through tenth items.

A twelfth item of the present disclosure includes the other of the magnet and magnet/ferromagnetic material located on a second portion of the planetary gear arrangement, and the twelfth item may be used in combination with any one or more of the first through eleventh items.

A thirteenth item of the present disclosure includes a magnet located on the transmission housing and the magnet/ferro-magnetic material located on the first portion of the planetary gear arrangement, and the thirteenth item may be used in combination with any one or more of the first through twelfth items.

A fourteenth item of the present disclosure includes a magnet located on a first carrier of the planetary gear arrangement and the magnet/ferro-magnetic material operatively associated with a planet of a second carrier, and the fourteenth item may be used in combination with any one or more of the first through thirteenth items.

A fifteenth item of the present disclosure includes the planet of the second carrier operatively associated with a pinion gear to supplement rotation of the input drive member, and the fifteenth item may be used in combination with any one or more of the first through fourteenth items.

A sixteenth item of the present disclosure includes an actuator that selectively advances and retracts the magnet/ferro-magnetic material of the planet toward the magnet of the first carrier, and the sixteenth item may be used in combination with any one or more of the first through fifteenth items.

A seventeenth item of the present disclosure is a method of varying speed output in a drive transmission assembly that includes providing a first drive member, providing a second drive member, and positioning a magnetic coupling between the first drive member and the second drive member to selectively vary the speed output of the second drive member relative to the first drive member.

An eighteenth item of the present disclosure includes placing one of a magnet and magnet/ferro-magnetic member in spaced relation in the magnetic coupling positioning step, and the eighteenth item may be used in combination with the seventeenth item.

A nineteenth item of the present disclosure includes selectively altering the spacing between the magnet and magnet/ferro-magnetic member to vary the magnetic coupling strength therebetween, and the nineteenth item may be used in combination with either or both of the seventeenth and eighteenth items.

A twentieth item of the present disclosure includes selectively moving one of the magnet and magnet/ferro-magnetic member toward and away from the other of the magnet and magnet/ferro-magnetic member, and the twentieth item may be used in combination with any one or more of the seventeenth through nineteenth items.

A twenty-first item of the present disclosure includes providing a primary pump member and driving an input shaft of the primary pump member via the first drive member, and the twenty-first item may be used in combination with any one or more of the seventeenth through twentieth items.

A twenty-second item of the present disclosure includes providing a secondary pump member and operatively driving the secondary pump member via the second drive member at a speed responsive to the magnetic coupling, and the twenty-second item may be used in combination with any one or more of the seventeenth through twenty-first items.

The disclosure has been described with reference to exemplary embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. For example, the description of a magnet on one component cooperating with a magnet or ferro-magnetic material on another component could be reversed. It is intended that the exemplary embodiments be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof. 

1. A variable output pump assembly comprising: an input drive member; a primary pump member operatively driven by the input drive member; a second drive member; and a variable torque coupling interposed between the input drive member and the second drive member to vary speed output of the second drive member.
 2. The variable output pump assembly of claim 1 wherein the coupling is a variable magnetic coupling interface between the input drive member and the second drive member.
 3. The variable output pump assembly of claim 2 wherein the magnetic coupling interface includes a magnet and a magnet/ferro-magnetic member in spaced relation and the spacing therebetween is selectively altered to vary the magnetic coupling strength therebetween.
 4. The variable output pump assembly of claim 3 wherein one of the magnet and magnet/ferro-magnetic member is operatively connected to an actuator that selectively moves the one of the magnet and magnet/ferro-magnetic member toward and away from the other of the magnet and magnet/ferro-magnetic member.
 5. The variable output pump assembly of claim 4 wherein the input drive member is connected to the primary pump member which includes a primary impeller, and a secondary pump member operatively driven by the second drive member at a speed responsive to the coupling.
 6. The variable output pump assembly of claim 5 further comprising a ring gear of a planetary gear assembly also operatively connected to the input drive member for rotation therewith.
 7. The variable output pump assembly of claim 6 further comprising a planetary gear operatively driven by the ring gear such that the secondary pump member that includes a secondary impeller operatively associated with the planetary gear assembly rotates at a different rotational speed.
 8. The variable output pump assembly of claim 7 wherein the carrier receives one of the magnet and the magnet/ferro-magnetic member and a fixed housing assembly receives the other of the magnet and magnet/ferro-magnetic member.
 9. The variable output pump assembly of claim 8 wherein the planetary gear assembly includes at least one planetary gear that receives a rotational drive input from the ring gear, and drives a sun gear in response thereto.
 10. The variable output pump assembly of claim 9 wherein the secondary impeller has an inlet receiving output flow from an outlet of the primary impeller.
 11. The variable output pump assembly of claim 2 wherein the magnetic coupling interface includes a magnet and a magnet/ferro-magnetic member, where one of the magnet and magnet/ferro-magnetic material is located on a first portion of a planetary gear arrangement.
 12. The variable output pump assembly of claim 11 wherein the other of the magnet and magnet/ferromagnetic material is located on a second portion of the planetary gear arrangement.
 13. The variable output pump assembly of claim 11 wherein the magnet is located on the transmission housing and the magnet/ferro-magnetic material is on the first portion of the planetary gear arrangement.
 14. The variable output pump assembly of claim 6 wherein magnet is located on a first carrier of the planetary gear arrangement and the magnet/ferro-magnetic material is operatively associated with a planet of a second carrier.
 15. The variable output pump assembly of claim 14 wherein the planet of the second carrier is operatively associated with a pinion gear to supplement rotation of the input drive member.
 16. The variable output pump assembly of claim 15 further comprising an actuator that selectively advances and retracts the magnet/ferro-magnetic material of the planet toward the magnet of the first carrier.
 17. A method of varying speed output in a drive transmission assembly comprising: providing a first drive member; providing a second drive member; positioning a magnetic coupling between the first drive member and the second drive member to selectively vary the speed output of the second drive member relative to the first drive member.
 18. The method of claim 17 wherein the magnetic coupling positioning step placing one of a magnet and magnet/ferro-magnetic member in spaced relation.
 19. The method of claim 18 wherein the spacing between the magnet and magnet/ferro-magnetic member is selectively altered to vary the magnetic coupling strength therebetween.
 20. The method of claim 20 further including selectively moving one of the magnet and magnet/ferro-magnetic member toward and away from the other of the magnet and magnet/ferro-magnetic member.
 21. The method of claim 17 further comprising providing a primary pump member and driving an input shaft of the primary pump member via the first drive member.
 22. The method of claim 21 further comprising providing a secondary pump member and operatively driving the secondary pump member via the second drive member at a speed responsive to the magnetic coupling. 